Field of the Invention
The invention relates to a motor vehicle seat with a back rest and a seat, which is supported by an adjustable underframe, which itself is supported via seat carriers of a longitudinal adjustment device.
With motor vehicle seats, an adjustment of the usable seat depth of the seat is desired, adjusting devices herefore are known from the state of the art. On the one hand motor vehicle seats can be counted to the latter, with which the actual length of the seat can be altered and also those, with which the back rest can be moved with regard to the seat in a relative movement in such a way that the seat depth used effectively is altered. The motor vehicle seat according to the invention belongs to the latter group.
It is desired to achieve a most possible comfortable, ergonomic seating position with motor vehicle seats by using simple mechanical means. Hereby, the normal dimensional relations of human beings are taken as a basis and by taking this relation into account, the possibilities for a seat adjustment can thereby be limited. With regard to this aspect, it is the aim of the invention to further develop the motor vehicle seat. It is therefore the task of the present invention to determine and further develop a motor vehicle seat in such a way that a most possible optimal adjustment of the back rest and the seat is achieved with regard to the desired seating position by using simple mechanical means.
Based on the motor vehicle seat of the above mentioned kind this task is solved in such a way that the back rest is supported by a back rest support which is connected to the back rest via a back rest mounting, that the back rest support is joined in a hinge with the seat carriers via front and back brackets of the back rest support and that the seat is joined in a hinge with the seat carriers via front and back brackets of the seat support in an adjustable way.
According to the invention the back rest and the seat are each arranged on individual four-bar linkages, especially joint parallelogram brackets, and they can also be interactively adjusted. These four-bar linkages are each regulated as well as set by an adjustment device, which is allocated to one of the four hinge points. Herefore different adjustment devices exist, which are known from the state of the art, for example adjustment devices with a sector gear and a pinion, eccentric adjustment devices and devices of a similar kind. As the back rest as well as the seat form a four-bar linkage together with each of the corresponding brackets and the seat carrier, a relative adjustment is possible between the back rest and the seat. Thereby the seat depth to be used can be adjusted by adjusting the seat in relation to the back rest or the back rest in relation to the seat.
In a preferred embodiment the four-bar linkages, with which the seat and the back rest support are connected with the seat carriers, are coupled in a compulsive action. As separate adjustment devices for the back rest on one hand and for the seat on the other hand are necessary with uncoupled four-bar linkages, this is not the case with coupled four-bar linkages, hereby only an adjustment device is necessary. Thereby the expenditure is saved and the operation is simplified. Therefore, in an especially preferred embodiment, the back support bracket of the back rest is comprised each in one piece with the left back support bracket of the seat support each, the same applies to the right back support bracket of the back rest and of the seat support respectively. The kinematics is thereby chosen in such a way that when adjusting the back rest and the seat to the front, the back rest is moved more strongly to the front than the seat, namely the usable seat surface is being shortened. Because of that in the course of the normal adjustment of a seat based on the position for larger people to the position for smaller people, the normal adjustment path of the seat is kept, but at the same time the back rest is moved to the front coupled in a compulsive action in such a way that the usable seat depth is shortened.
The coupling of both four-bar linkages can occur in various ways. The decisive factor in the concept of the coupling is to make sure that always a shifting of the scat by a path x corresponds to a bigger shifting distance y of the back rest. This may occur for example by the fact that the seat is moved on a smaller arc of a circle than the back rest, the effective length of at least one bracket of the seat support is distinctly shorter than that of the corresponding bracket of the back rest support. It may also occur by the fact that the brackets are arranged in such a way that when the seat is adjusted at least one bracket of the seat support moves essentially crosswise to the seat carriers, but not in their longitudinal direction, while the corresponding bracket of the back rest support moves essentially parallel to the seat carriers. These kinematics can also be achieved for example by an offset angle of the respective brackets against each other.
In a preferred embodiment at least one pair of brackets of the seat support, preferably both front brackets of the seat support are embodied as an adjustable pair of articulated levers synchronized with each other. That way the height of the front edge of the seat can be altered and set independently from the other adjustments. But nevertheless in the use of the language of the existing text, a four-bar linkage exists, because the two levers of the pair of articulated levers, which together realize the respective bracket, are only adjusted against each other for the adjustment of the front edge of the seat, after the adjustment has been completed however, they form one single bracket again.